P0300 After 2 runs at dragway - UPDATE 8/14/24

[2ndAmend]

Very sorry to bother you guys with a new question/problem already. I leave for Land Speed Trials Tuesday morning and today it threw a P0300.

I wanted to test the Sunoco 100 octane before I left to make sure the Stage 2 didn't kick out of 100 mode. I did 2 passes, no problem, it stayed in 100 mode through the run and back to the pits. I inflate the DR's and drove off for home, then noticed the CLE. And it refused to go into 100 mode saying "System Fault, High Octane Mode Disabled".

Got home and scanner said:

7E8 Engine, P0300
7E9 A/T, no other information

I only have a couple days to solve this so I am posting this before reading the 10,000 posts on this code. If I can't run the car next week I'm screwed.

I'll start researching and hope someone may have a shortcut. I'm tempted to reset and go.

 

[DGatzby]

Misfire code, it may be lots of things. Or nothing, sometimes they error off when ran hard. If you are confident your systems are correctly working and no other problems are present then…Reset and drive for a while b4 then and see if it comes back. Do some aggressive pulls. My Hellcat did that when lapping very aggressively years ago. But it cleared up later itself.

That sounds like a PIA for you, good luck.

 

[2ndAmend]

Misfire code, it may be lots of things. Or nothing, sometimes they error off when ran hard. If you are confident your systems are correctly working and no other problems are present then…Reset and drive for a while b4 then and see if it comes back. Do some aggressive pulls. My Hellcat did that when lapping very aggressively years ago. But it cleared up later itself.

That sounds like a PIA for you, good luck.

Thanks. Choice now is reset and hope, or see if a dealer will look at it before Tues, which is expecting a lot from a dealer these days.

On the first attempt at the 2nd run the Line Lock wouldn't work, then it did, and wouldn't let go. I went back to the pits, let it cool a bit then restarted, everything ok, then did the 2nd run. I can't imagine it's related but computers can do some strange things.

 

[Unholy707]

Send it

 

[2ndAmend]

Send it

?

 

[vortecd]

Thanks. Choice now is reset and hope, or see if a dealer will look at it before Tues, which is expecting a lot from a dealer these days.

On the first attempt at the 2nd run the Line Lock wouldn't work, then it did, and wouldn't let go. I went back to the pits, let it cool a bit then restarted, everything ok, then did the 2nd run. I can't imagine it's related but computers can do some strange things.

What you said computers can do strange things. Make sure your battery is good, that is one cause of the computer not acting right.

Some times can be tough to find a misfire. It didn't come up as a certain cylinder so that may be a sign of something random. This is why you would want to datalog because it may show up somewhere

 

[2ndAmend]

What you said computers can do strange things. Make sure your battery is good, that is one cause of the computer not acting right.

Some times can be tough to find a misfire. It didn't come up as a certain cylinder so that may be a sign of something random. This is why you would want to datalog because it may show up somewhere

I inflated the tires so it was running on the battery for maybe 15-20 min before it happened. Also I disconnected the battery a couple times last week trying to figure the vented seat problem. Maybe it hasn't fully recovered.

Put a meter on the battery, 12.4 connected, trunk light on, engine off, should be ok. OEM battery is just over 2 years old.

I'm thinking reset the codes in the morning.

 

[fumanchu182]

I had a misfire on cylinder 8 when I started to go past 18psi. Now it's permanent, funny part is the car is rolling like a god damn champ so I know I am at the limits of the PCM.

 

[2ndAmend]

Cleared the codes, disconnected the battery, changed tires, cleaned the posts, reconnected battery, everything looks good now, and it accepts 100 octane mode. As soon as it stops raining and the roads dry a bit I'll go waste a few gallons of 100.

Funny thing, this time when I reconnected the battery, the proper screen came back, I did not get the dark blue screen like I did when working on the seat venting. I'm hoping the PCM was unhappy after the seat vent problem and maybe now it's happy? Or maybe the ragged current draw of the tire inflater caused a problem? I hope to try it in an hour or two.

Thanks for the help, I'll let you guys know.

 

[2ndAmend]

Drove 50 miles or so, did many pulls, several limit of traction to 85-90, all is well. Looks like the PCU might have puked yesterday but seems fine now. Fingers crossed I'm going as is. Thanks everyone for the help and suggestions, again!

 

[2ndAmend]

I'm thinking that all cars should have a "REBOOT" button! Every electronic device should have one!

My stupid new printer doesn't have the DIN connector in the back, the power cord is hard wired! Now I have to go to the power strip to unplug it to knock some sense back into it!

 

[2ndAmend]

My security camera DVR was screwing up. I unplugged and re-plugged several times, it would work for a while, then screw up again. I went through the menus and found the "reformat HD". I did that and it now works perfectly.

Seems every electronic device needs an enema once in a while...

 

[SilverBillet]

I'm thinking that all cars should have a "REBOOT" button! Every electronic device should have one!

My stupid new printer doesn't have the DIN connector in the back, the power cord is hard wired! Now I have to go to the power strip to unplug it to knock some sense back into it!

I think there is a way to reboot it?

 

[16GoManGoHC2]

At the very least pull the plugs and inspect them, all 16, BEFORE beating on it anymore.

 

[EricG]

At the very least pull the plugs and inspect them, all 16, BEFORE beating on it anymore.

How much of a pain is it to check/change plugs on a Hellcat? I've read it is a pain in the a$$ due to an intercooler line? I am at 40k miles and plan on doing my spark plugs next - dealer said 50k is the recommended interval. But anyway when I was discussing it with my service advisor I told him I heard it was difficult and different that the 5.7/6.4 - and he was like naw...spark plugs on these Hemis is pretty easy. What is the real story?

 

[vortecd]

How much of a pain is it to check/change plugs on a Hellcat? I've read it is a pain in the a$$ due to an intercooler line? I am at 40k miles and plan on doing my spark plugs next - dealer said 50k is the recommended interval. But anyway when I was discussing it with my service advisor I told him I heard it was difficult and different that the 5.7/6.4 - and he was like naw...spark plugs on these Hemis is pretty easy. What is the real story?

Nothing like a 5.7. The coil pack face down which it harder to unplug and the hump in valve cover makes it more difficult. 5.7 is easy
If I recall it took me an hour to do plugs on my jeep and 5 on the hellcat. I fought getting the coil pack wire off. Intercooler lines will move out of the way. Other issue is the wiring running on the passenger side next to engine

 

[GNBRETT]

Change ur plugs!

 

[DGatzby]

Nothing like a 5.7. The coil pack face down which it harder to unplug and the hump in valve cover makes it more difficult. 5.7 is easy
If I recall it took me an hour to do plugs on my jeep and 5 on the hellcat. I fought getting the coil pack wire off. Intercooler lines will move out of the way. Other issue is the wiring running on the passenger side next to engine

That don’t sound fun. My local dealer rates are now $205/hr, which sucks. Glad I only have about 10k on the engine right now @EricG.

 

[16GoManGoHC2]

How much of a pain is it to check/change plugs on a Hellcat? I've read it is a pain in the a$$ due to an intercooler line? I am at 40k miles and plan on doing my spark plugs next - dealer said 50k is the recommended interval. But anyway when I was discussing it with my service advisor I told him I heard it was difficult and different that the 5.7/6.4 - and he was like naw...spark plugs on these Hemis is pretty easy. What is the real story?

2-3 hour job with the right tools. Drivers side pretty easy, passenger side just unbolt the coolant tanks 10 mm nuts and and bungee cord it up and out of the way. Look at posts I’ve made on doing it for tools needed to make it easier.

 

[vortecd]

Next time I have to do it I know some coils, maybe all you don't have to unplug them just move them to get the plugs out. If they need to come out after the coil is out you can flip it around to unplug it